is called Petrichor, and it is caused by Geosmin.
Geosmin is an organic compound with the formula C12H22O. It’s produced by several classes of microbes, including cyanobacteria (blue-green algae) and actinobacteria (especially Streptomyces), and released when these microbes die. The human nose is extremely sensitive to geosmin and is able to detect it at concentrations as low as 5 parts per trillion.
Can’t trust a clam farther than you can throw it, especially when salt is concerned, apparently.
Actually, I’m not sure if this video proves anything (what would happen if there was sugar on the table, or brownie crumbs, or cinnamon?) but it is pretty awesome. (via ★asimone)